1. Field
Embodiments of the present invention relate to an organic light emitting display.
2. Description of the Related Art
Recently, various flat panel displays (FPDs) capable of reducing weight and volume that are disadvantages of cathode ray tubes (CRTs) have been developed. The FPDs include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays.
Among the FPDs, the organic light emitting displays display images using organic light emitting diodes (OLED) that generate light by re-combination of electrons and holes. The organic light emitting display has high response speed and is driven with low power consumption.
In general, OLED displays are divided into passive matrix type OLED (PMOLED) displays and active matrix type OLED (AMOLED) displays according to a method of driving the OLED.
The AMOLED type display includes a plurality of gate lines, a plurality of data lines, a plurality of power source lines, and a plurality of pixels coupled to the above lines to be arranged in the form of a matrix. In addition, each of the pixels typically includes an OLED, two transistors (e.g., a switching transistor for transmitting a data signal and a driving transistor for driving the EL element in accordance with the data signal), and a capacitor for maintaining the data voltage.
The AMOLED type display typically has low power consumption. However, the intensity of current that flows through the OLED varies with deviation in a voltage between the gate and source of the driving transistor for driving the OLED. That is, variations in the threshold voltage of the driving transistor can cause non-uniformity in the display.
Because the characteristics of the transistors provided in each of the pixels vary with manufacturing process variables, it is difficult to manufacture the transistors so that the characteristics of all of the transistors of the AMOLED are the same. Therefore, deviation in the threshold voltages of the pixels exists.
In order to reduce or solve such a problem, research on a compensation circuit including a plurality of transistors and capacitors is being performed. The compensation circuit can be formed in each of the pixels. However, in this case, a large number of transistors and capacitors are to be included in each of the pixels.
To be specific, when the compensation circuit is added to each of the pixels, the transistors and capacitors that constitute each of the pixels and signal lines for controlling the transistors are added so that, in the case of a bottom emission AMOLED type display, an aperture ratio is reduced and the possibility of manufacturing defects increases as the number of components of the circuit increase and become more complicated.
In addition, in order to reduce or remove a motion blur phenomenon, high speed scan driving of no less than 120 Hz may be used. However, in this case, charge time per each of the scan lines is significantly reduced. That is, when the compensation circuit is provided in each of the pixels so that a large number of transistors are formed in each of the pixels coupled to one scan line, capacitive load increases. As a result, it is difficult to realize the high speed scan driving.